Quantitative Risk Assessment And Regionalization Of Geohazards At Different Scales

Geological hazard risk assessment and zoning are the basis of formulating geological hazard prevention and control countermeasures.The risk assessment and regionalization of geological disasters at different scales can provide the basis for formulating the prevention and Control Countermeasures of geological disasters at different levels.Quantitative risk assessment and regionalization of geological hazards is one of the hot and difficult issues in the study of geological hazards.Longnan area of Gansu Province is one of the areas where landslides and debris flows occur frequently in China.Taking Xihe County in Longnan County of Gansu Province as an example,this paper takes the relatively densely populated market town contiguous area and the most densely populated Hanyuan town as the study area of 1:50000 and 1:10000 scales respectively,adopts the risk assessment method and vulnerability assessment model suitable for the types of geological disasters and the characteristics of affected objects in the area,and then according to the international general risk = risk × Vulnerability model,quantitative assessment and zoning of geological disaster risk at different scales.1.According to the landslide and debris flow disaster types in the study area,scoops3 d and TRIGRS,which are suitable for deep landslide and shallow landslide,are used to evaluate the stability of the slope in different scales and conditions,and flow-2d is used to simulate the activity intensity of debris flow in different scales and conditions.Based on the results of numerical simulation,the risk of different types of geological disasters in different sections is quantitatively evaluated.The evaluation results show that:(1)At 1:50000 scale,the high risk area of landslide in Lianpian District,Jizhen District,Xihe county is concentrated in the middle and lower slope section,Banqiao Village slope and Lushan village slope,etc.,and the range of dangerous areas increases with the increase of rainfall intensity;The high risk areas of debris flow are concentrated in DUJIAGOU,shanyugou,Luhe ditch and accumulation area.With the increase of rainfall intensity,the debris flow of DUJIAGOU flows to Yangshui River,which may block the Yangshui River on the right side of the gully mouth to form a dam plug.(2)Under the scale of 1:10000,the high risk area of landslide in Hanyuan town is located in the middle and lower reaches of Baifeng gully and the slopes on both sides of the gully mouth,Zhaojia slope on the west side of mengmo village,west slope of Wulipu village and Dongshan slope on the east side of Chaoyang community;The debris flow in Baifeng gully reaches the Bank of Yangshui River along the northeast direction after it washes out of the gully.The high risk area is concentrated in the middle of Nanguan village.With the increase of rainfall intensity,the scope of debris flow deposition increases,which may form a barrier dam.2.According to different scales,the vulnerability evaluation indexes with different degrees of precision are selected.Based on field investigation and combined with high-definition remote sensing data,different types and different degrees of precision of disaster bearing body identification and vulnerability zoning are carried out.The results of vulnerability assessment showed that:(1)At the scale of 1:50000,the high vulnerable areas in the contiguous area of Xihe town are mainly located at the gully mouth and slope toe of debris flow on both sides of Yangshui River,expressways and national highways,schools,factories,shopping malls and residential areas in the center of Hanyuan town.(2)Under the scale of 1:10000,the high vulnerable areas of assets in Hanyuan town are mainly concentrated in Fengshan community and Nanguan community,where government agencies,schools and residential areas are concentrated,low rent housing areas in the southeast of Hanyuan town and some g7011 Expressway sections;High vulnerable areas are mainly concentrated in Fengshan community,Nanguan community,low rent housing community and Hanyuan junior high school.3.Based on risk = danger × Based on GIS tools and Arc GIS platform,the vulnerability evaluation model is superimposed to obtain the comprehensive risk zoning of Xihe County town contiguous area at 1:50000 scale and the asset and population risk zoning and quantitative risk value of Hanyuan town at 1:10000 scale under different working conditions.The results of risk assessment show that:(1)Under the scale of 1:50000,the high-risk areas in the contiguous areas of market towns in Xihe county are concentrated in Laozhuang village,Qiaobao new village,Yuming village,huangjiamo village,baijiashan village,Baifeng village,Shangcheng village,Banqiao Village and Matai village.Most of the high-risk areas are the result of the grid superposition of high-risk areas and medium vulnerable areas,among which Shili village,Baifeng village,Shangcheng village,Banqiao Village and Matai village Duhe village,Fengshan community and Nanguan community increased with the increase of rainfall intensity,which are the areas with high risk and high vulnerability.(2)Under the scale of 1 : 10000,the high-risk areas of assets and population in Hanyuan town are mainly concentrated in Baifeng village,baijiashan village,Nanguan village and Nanguan community.With the increase of rainfall intensity,Fengshan community is threatened.Most of the high-risk areas are the result of grid superposition of high-risk areas and medium vulnerable areas,Among them,the grids of local high-risk areas in Nanguan community and Fengshan community are the grids of high-risk and vulnerable areas at the same time.The potential asset loss and population casualty values of Hanyuan town under 20-year,50 year and 100 year return period rainfall conditions are 268.69 million yuan and 1593 people per year,397.59 million yuan and 4145 people per year,571.79 million yuan and 5292 people per year,respectively.